Encapsulation is the process of covering electronic components in a protective shell in order to prevent physical damage following die and wire bonding. One type of encapsulation is referred to as dam-and-fill.
Dam-and-fill encapsulation provides a dam around the periphery of a component for the purpose of preventing flow of the encapsulant to adjacent components. There are several different types of dams that can be used. For example, mechanical dams serve as physical walls that are built into the substrate around the die placement area, whereas silicone and double viscosity dams include a line of silicone or high-viscosity encapsulant that is dispensed around the periphery of the component. In each case, a low-viscosity encapsulant (i.e., a liquid fill) can then be dispensed over the component so as to fill the area of the dam. The liquid fill encapsulant thus encapsulates and protects the die and wire bonds.
Dam-and-fill techniques can be used, for example, to encapsulate various parts of compact optoelectronic modules. For example, as shown in FIG. 1A, dam-and-fill techniques can be used to provide encapsulation 10 for wires 12 and bond pads 14, or other electronic components 16, on a printed circuit board (PCB) substrate 18 on which an optoelectronic module 20 is mounted. In the illustrated example, the module 20 is a compact camera module that includes a lens stack 22 disposed over a transparent substrate 24, which separates the lens stack 22 from an image sensor 26. The wires 12 electrically couple the image sensor 26 to the bond pads 14 on the PCB substrate 18.
In some cases, as shown in the example of FIG. 1B, it may be desirable to make the width of the lens stack 22 and the transparent substrate 24 wider than the image sensor 26 so as to obtain a wider field of view. However, such situations can raise challenges in using dam-and-fill techniques to encapsulate the wires 12 and bond pads 14. In particular, difficulties can arise because the wires 12 and bond pads 14 are located in a space beneath the transparent substrate 24, where it is difficult to introduce the encapsulant. Yet, if that space is not completely filled, the bond wires 12 may not be entirely embedded within the encapsulant, and the module may not be sufficiently rigid or stable.